The present invention relates to a recording head for discharging ink comprising a coloring agent dispersed in solvent to thereby record on a recording medium, and an ink jet recording apparatus using the recording head.
Conventionally, an ink jet recording apparatus, which discharges a small quantity of ink droplets through a minute discharge port to cause the ink droplets to adhere onto a recording medium for printing an image, has been configured by conducting ink to each discharge port from an ink tank, and imparting kinetic energy to the ink to thereby cause ink droplets to be discharged through the discharge ports and to adhere onto the recording medium for forming dots.
As one of driving methods to impart kinetic energy to the ink, there is a system (electrostatic recording system) in which voltage is applied between a recording electrode and a common electrode, with which a recording medium comes into contact, to cause ink to be discharged by means of an electrostatic force. This system has long attracted attention as a method to realize a highly precise ink jet printer because an amount of ink to be discharged onto the recording medium can be controlled by pulse width modulating voltage to be applied to the recording electrode.
As an example of such a system, there is described, in WO97/27058 specification, a method in which ink comprising a coloring agent dispersed in a low density in solvent is supplied to grooves, and voltage is applied to a recording electrode provided on the surfaces of walls of the grooves to condense the coloring agent with charge by an electric field for discharging the ink condensed toward the recording medium from the recording electrode.
Also, in JP-A-11-10911 specification, there has been described an ink circulation method in a recording apparatus having the above described system. In the present specification, it has been described that it is possible to prevent pressure fluctuation in the ink circulation path by the provision of air chambers at positions before ink is supplied to an ink flying unit and after the ink is recovered from the ink flying unit.
The electrostatic recording system disclosed in the above described specification is a method for discharging ink obtained by concentrating the coloring agent component onto the recording medium for recording an image by applying bias voltage to the recording electrode while the ink is being circulated, gathering the ink obtained by concentrating the coloring agent component to the tip end of the recording electrode, and superimposedly applying the pulse voltage to the recording electrode in the state. Also, since there are not present small holes in the ink discharge unit in the present recording system, it is difficult to create clogging due to ink. For the reason, even if a long recording head having a number of recording electrodes of several thousands is manufactured, it is difficult to cause defective points where the ink does not fly, and therefore, this is an advantageous recording method to realize an ink jet recording apparatus having a long recording head. Since the recording apparatus having the long recording head is capable of recording many dots at the same time, this is characterized by being able to perform high-speed printing. In order to actually realize the long recording head, it is necessary that all of a multiplicity of ink discharge units is manufactured without defects, and that all the ink discharge units have the same printing characteristics during printing. For this end, it becomes important that the multiplicity of recording electrodes and ink flow paths are the same in shape, and that the recording head can be simply configured at low price.
According to the present invention, an ink jet recording apparatus having a better electrostatic recording system than the above described prior art has been devised, and one of objects of the present invention is to provide a small-sized low-priced recording head.
Another object is to provide a recording head capable of recording a high-quality, highly precise image at high speed and an ink jet recording apparatus using the same.
That is, according to an embodiment of the present invention, the configuration is arranged such that there are provided a first ink chamber and a second ink chamber, each containing ink comprising the coloring agent dispersed in solvent and an ink discharge unit for discharging the ink, and that the first ink chamber is arranged above the ink discharge unit, and the second ink chamber is arranged below the ink discharge unit.
Also, the configuration is arranged such that the ink flows from the first ink chamber to the second chamber due to differences in height of the positions whereat the first ink chamber, the ink discharge unit and the second ink chamber are arranged.
Also, the configuration is arranged such that an ink flow rate adjusting unit is provided between the first ink chamber and the ink discharge unit, and between the ink discharge unit and the second ink chamber respectively.
Also, the configuration is arranged such that a minimum value S1 of the sectional area of the ink flow path upstream of the recording electrode, a sectional area S2 of the ink flow path at the tip end of the recording electrode and a minimum value S3 of the sectional area of the ink flow path downstream of the recording electrode satisfy relation of S3 greater than S1 greater than S2.